1. Technical Field
The present disclosure relates generally to electrosurgical instruments and, more particularly, to an open or endoscopic bipolar electrosurgical forceps and system and method of manufacturing thereof.
2. Background of Related Art
A hemostat or forceps is a simple pliers-like tool that uses mechanical action between its jaws to constrict vessels and is commonly used in open surgical procedures to grasp, dissect and/or clamp tissue. Electrosurgical forceps utilize both mechanical clamping action and electrical energy to effect hemostasis by heating the tissue and blood vessels to coagulate, cauterize and/or seal tissue.
Over the last several decades, more and more surgeons are complementing traditional open methods of gaining access to vital organs and body cavities with endoscopes and endoscopic instruments which access organs through small puncture-like incisions. Endoscopic instruments are inserted into the patient through a cannula, or port that has been made with a trocar.
By utilizing an electrosurgical forceps, a surgeon can either cauterize, coagulate/desiccate and/or simply reduce or slow bleeding, by controlling the intensity, frequency and duration of the electrosurgical energy applied through the jaw members to the tissue. The electrode of each jaw member is charged to a different electric potential such that when the jaw members grasp tissue, electrical energy can be selectively transferred through the tissue.
Electrosurgical methods may be able to seal large vessels using an appropriate electrosurgical power curve, coupled with an instrument capable of applying a large closure force to the vessel walls. It is thought that the process of coagulating small vessels is fundamentally different than electrosurgical vessel sealing. For the purposes herein, “coagulation” is defined as a process of desiccating tissue wherein the tissue cells are ruptured and dried. Vessel sealing is defined as the process of liquefying the collagen in the tissue so that it reforms into a fused mass. Thus, coagulation of small vessels is sufficient to permanently close them. Larger vessels need to be sealed to assure permanent closure.
In order to properly and effectively seal larger vessels, a greater closure force between opposing jaw members is required. It has been found that the pressure range for assuring a consistent and effective seal is between about 3 kg/cm2 to about 16 kg/cm2 and within a working range of about 7 kg/cm2 to about 13 kg/cm2. Manufacturing an instrument which is capable of providing a closure pressure within this working range has been shown to be effective for sealing arteries and other vascular bundles.
Various force-actuating assemblies have been developed in the past for providing the appropriate closure forces to effect vessel sealing. Due to exact forces that need to be applied to the opposing jaw members, during assembly of the sealing instrument, it would be an advantage to test the closure pressure between sealing surfaces to assure that the closure pressure falls within the preferred pressure range for sealing tissue and vascular bundles. Unfortunately, it has been found that measuring the closure pressure between the sealing surfaces is particularly difficult. For example, one of the inherent difficulties of accurately measuring the closure force includes measuring the closure force in a non-destructive fashion, e.g., placing a measuring device, such as a strain gauge or pressure sensitive film, between the jaw members interferes with the final angle of the jaw members, interfering with the measurement. The measurement device would need to be shaped exactly like the jaw profile in order to measure the pressure accurately. The jaw would have to be free of stop members or only the peaks in pressure would be measured. Moreover, it has been found that manufacturing tolerances of the internal working components of the handle assembly and actuating assemblies may affect the overall closure pressure between the sealing surfaces.